[ Vangeance gives a brief hum in thought, looking down at his hand; thin wisps of light pull from his fingertips. ]

I cast spells by manipulating mana -- energy present in myself, the atmosphere, and in all things.

[ The glow fades, and he lowers his hand. A slow exhale before he continues, keeping his answer plain and honest: ]

I would attempt to channel mana from the environment and use it to enhance the plant's mana, making them stronger or duplicating them. But ... I've never attempted to combine my magic with something from another world before, so I'm unsure how they'll interact. And mages of my kind are somewhat limited in our abilities unless we can manifest our attributes. Completely preventing my trees from mingling with your plants may be difficult.